Fine tuning polymer-based biomonitoring tools for quick and cost-effective screening of contaminants in lipid containing matrices
Supervisor: Caroline Gaus (National Research Centre for Environmental Toxicology (Entox), The University of Queensland)
Persistent, bioaccumulative and toxic compounds (PBTs) are among the most hazardous compounds for humans and marine wildlife. Quantifying organism exposure to PBTs is time consuming and costly, and traditionally requires chemically targeted extraction and clean up. New polymer-based passive samplers that have the potential to overcome these limitations have recently been developed. The aim of the present study was to further test the applicability of these novel tools for passive sampling of PBTs in lipid rich tissues, and to evaluate whether fine-tuning of the polymers can be used to further enhance their performance (i.e. high sorptive capacity and low lipid swelling) as biomonitoring tools. Using polydimethylsiloxane (PDMS) as solid substrate, a set of methacrylate based polymers with different functional groups, monomer concentrations and degree of cross-linking were developed using graft polymerization in collaboration with AIBN, UQ. Their chemical sorptive capacity and lipid swelling concentration was tested via batch experiments to quantify Klipid-polymer using PCDDs and PCBs as test compounds. Initially, polymer lipid swelling kinetics and swelling equilibrium was quantified in different matrices. Among the various polymers tested, poly-butyl methacrylate (PBMA) showed the highest sorptive capacity, which increased with increasing monomer (e.g. the concentration of PBMA monomer grafting increases from 1 M to 4M, Klipid-polymer decrease from 2.43 ± 0.61 to 1.58 ± 0.04). Lipid swelling of polymers was independent of the percent lipid content and type of tissues, but higher sorptive capacity was generally associated with an increase in lipid mass transferred into polymers, which results in undesirable matrix components in the sampler extract. However, lipid swelling equilibrium concentrations of PBMA could be considerably reduced by increasing the degree of polymer cross-linking, presumably due to the associated decrease in pore sizes of the polymer net-work and exclusion of typically large (70-100 Å) storage lipids. Tighter cross-linking did not affect the chemical sorptive capacity of the polymer grafts. The lipid swelling concertation was minimized beyond 15% of custom-made cross-linking. The sorptive capacity of PBMA 4 M with 15% crosslinked was consistent and sufficiently high to bio-monitor tissues containing typical PBT background levels. The polymer solubility (SPolymer) of PBMA with 15% and 20% crosslinking that were coated directly on silicon wafer without PDMS substrate shows 10 times higher sorptive capacity compared to PBMA 4M and down the detection limit to 1 pg/glipid (limit of instrument detection 100 fg, 1 μl injection and 20 μl extracts). Overall, the results of the present study provides information that facilitates fine-tuning of PBMA based samplers to offer a simple, quick and cost-effective tool for biomonitoring of mixtures of PBTs in lipid containing matrices.